Manufacture of cellulose esters



Patented Aug. 1, 1950 MANUFACTURE OF CELLULOSE ESTER/S" Charles Doras, Dijon, France, assignor to Societe Rhodiaceta, Paris, France, a French company No Drawing. Application March 8, 1950, Serial.

. No. 148,520. In France February 8, 1946;

1 The present invention relates to the manufacture of "cellulose esters by processes in which the esterified cellulose is soluble in the esterifieation mixture and it has particular relation to the manufacture of cellulose esters which contain at least one acyl radical containing more than four carbon atoms.

In the previously known esterification processes of the above mentioned type, the ester produced dissolves in the esterification mixture and remains in this solution until the end of the esterification so that the first portions of the ester to be formed remain subjected to the action of the reagents until the whole of the cellulose has become esterified and dissolved. As a consequence of this, the first and major part of the cellulose ester formed undergoes a degradation which is harmful to the quality of the products prepared from such esters.

According to the present invention cellulose is esterified by means of an esterification bath capable of dissolvin the cellulose derivative formed, but, in contrast to the before-mentioned known processes, as the cellulose derivative is formed and goes into solution, this solution is separated from the rest of the reaction mass and subjected toa treatment which prevents appreciable degradation of the cellulose derivative already formed, whereas in the non-completely esterified and undissolved residue the reaction continues until esterification and solubilization of the whole of the cellulose takes place.

In order to stop the reaction in the solution of the esterified product and to prevent the before-mentioned known method can be used, such as for example destruction of the excess of the esterifyingreagent or destruction of the reaction catalyst.

In carrying out the process of the present invention, the esterifying bath can be brought in contact with the cellulose in any suitable appa ratus, for example an apparatus containing a filtering device, through which the solution of the cellulose ester formed can be passed, in which, however, those cellulosic fibres which have not been completely esterified yet, are retained. These fibres are swollen and impregnated by the esterification mixture and remain, therefore, exposed to reaction of the esterifying agents so that their esterification continues. As soon as the cellulose ester is formed, it passes into solution and this solution then emerges from the filtering device and is treated to stop further reaction in the solution. Meanwhile the reaction in the residue goeson until all the cellulose which has been degradation of the ester, any

9 Claims. (01. 260- 225) introducedinto the reaction mixture is esterified and goes into solution as esterlfication proceeds.

The apparatus of the above mentioned type used for the separation of cellulose ester solution from the undissolve'd, not completely esterified cellulose material may, for example, consist of a system of wire gauze or filters consisting of textile materials resistant to the esterification bath, layers of sand, metallic turnings or Raschig rings or the like.

The invention may be applied to continuous esterification processes and also to discontinuous operation.

The following examples illustrate the method:

of the invention byway of example Without liIniting it in any respect. The parts are by weight unless otherwise stated.

Example 1 A continuously prepared mixture containing 100 parts of cellulose previously subjected to a usual pretreatment'with 50 partsof acetic acid Of i I 200 parts of caproic acid (Cal-11202) 250 parts acetic anhydride, and

14 parts of concentrated sulfuric acid,

is subjected to. begining acetylation during a period of 10 minutes in an apparatus for continuous acetylationof thetype described in U. .8. PatentNo. 1,859,579. The fibrous mixture emerging from this apparatus is supplied by means of a piston pump under a pressure of 45-50 kg. per squarecm to a column containing stacks of wire gauze bath is passed through the filter system.

The tri-ester solution emerging from the col umn is mixed immediately with of its weight of acetic acid of It is than subjected to ripening and finally precipitated by the addition ofwater. j

The cellulose aceto-caproate thus obtained has very satisfactory properties and is distinguished from an acetocap roate obtained under otherwise equal conditions in a known manner, i. e. without the application of the fractional withdrawal according to the present invention of solution of the reaction product formed, by a substantially increasedviscosity of solutions of the end product in organic solvents. w j

Example 2 100 parts of cellulose are pretreated for 30 minutes at about C. with 50 parts of acetic acid of 100%, containing 1 part of sulfuric acid. The cellulose thus pretreated is passed continuously through an apparatus which is provided with a stirrer and into; which the following two mixturesare supplied separately:

M feature 1:

'200 parts of acetic anhydride,

100 parts of stearic acid (CisHisOz), and 250 parts of acetic acid of 100%.

Mixture 2:

100 parts of acetic acid of" 100%, 8 parts sulfuric acid of- 66 B'.', and" 3 parts of perchloric acid of 65%.

The pasty mass thus obtained is continuously introducedinto and passed through.acolumnpro-- vided with a filtering network similar to that.

ment untilan acetone-solublecellulose aceto stearate is formed.

Example 3.

IO'Oparts of'cellulose are pretreated for minutes-atabout 25 C. with-.50 parts of acetic acid of11 .00%., containing. 1 part of sulfuric acid. The

through an apparatus whichiisprovided with a stirrer and into which the following two mixtures are supplied separately:

Mixture-'1 200 parts of acetic anhydride', 'lO' parts of lauric acid (C12H24O2) and 250 parts of acetic acid of 100%.

Mixture 2:

100 parts of acetic acid of? 100%, 8 parts of sulfuric. acid of 66 Be, and. 3 partsof. perchloric acid .of 65 The pasty massthus obtained: is: now further:

treated and an acetone-soluble cellulose acetolaurate is' obtained in the manner described in thepreparation of cellulose aceto-stearate lnEX" ample 2-;

Example 4 100 parts of cellulose are pretreated for 30 minutesat about 25 C. with. 50=parts of acetic acid of 100%,,containingv lpart of sulfuric acid. The cellulose thus pretreated is passed continuously" through anapparatus which is provided with a stirrer and into which'the following two mixtures are supplied separately:

Mixture 1:

200 parts of acetic anhydride,

90parts of palm'itic acid (C16H3202) 250 parts of acetic acid of 100%.

Mixture 2:.

100 parts of aceticacidof 100%,

8-partsof sulfuric acid of 66 B., and 3-parts ofperchloric acid of. 65%.

The cellulose esters obtained according to Examples 2, 3 and 4 are distinguished by the absence of degradation demonstrated by increased viscosity of their solutions in comparison to products prepared under otherwise equal conditions but without the application of the present invention.

Example 5 A mixture of the following composition is introduced by continuous supply into a mixing device provided with a stirrer and capable of being heated by means of a double wall, the temperature being maintained at 55 (3.:

Parts fiellulose 100 Monochloroacetic acid 25 Palmitic anhydride 1400 Carbon tetrachloride 1300 The mass removed from the'lower partof this mixer is introduced by means of ahelical pumpf int-o a second apparatus whichis maintained'at a temperature of 60 C; and in which parts of i methanesulfonic acid are added in a continuous quently, the'mass is introduced into a filtering network similar to. that" used according'to the" above Example 1., maintained at a temperature:

The clear solution of cellulose tripalmitate'thus;

cellulose thus, pretreated is. passed continuously I Obtained is precipitated by the addition of: Water in proportion as it emerges from the filtering net.-

work. It is an undegracledproduct of high:

viscosity;

Example 6 A reaction mixture-is continuously prepared by mixing; the following ingredients in the followingv proportions:

Parts by weight Myristic acid (Cid-H802) 250 Cotton pretreated in customary manner 40 Chloroacetic anhydride 600 Magnesium perchlorate Esterification of the cotton cellulose in this mixtureis carriedout at 60-65 C. substantially in the manner described in the above Example 1.

Example 7 500 lbs. ZOO-lbs. 700 lbs.

2 lbs. lbs.

ethoxy acetic anhydride,

acetic anhydride,

stearic acid,

paratoluene sulfochloride, cellulose pretreated in the. usual manner.

Example 8' A reaction mixture is continuously prepared by mixing the following ingredients in the following proportions:

Parts by weight Pelargonic acid (C9H1802) 250' Cellulose pretreated in customary manner 50 Chloracetic anhydride 6.0.0

Magnesium perchlorate 1.5

Es'terification iscarried out at 60-"-65 C. by-

following the procedure described in the above Example 1.

Example 9 An esterification mixture is continuously prepared and treated in the manner described in Example 1, from the following ingredients:

700 lbs. prcpoxy acetic anhydride 200 lbs. acetic anhydride 700 lbs. stearic acid 100 lbs. molten zinc chloride, and

100 lbs. cellulose pretreated in customary manner.

ester. The esters obtained according to Examples 6-9 are likewise distinguished by high quality, particularly high viscosity of their solutions.

As shown by the above examples, in carrying out the present invention any fatty acid having in the molecule more than 4 carbon atoms, particularly 5 to 18 carbon atoms, may be used, if desired in combination with other lower or higher fatty acids.

It will be understood that this invention is not limited to the specific steps, substances and con ditions described above and may be carried out with various modifications without departing from the scope of the invention as defined in the appended claims.

Reference is made to my co-pending application Ser. No. 725,284, filed on January 30, 1947, of which this is a continuation-in-part.

What is claimed is:

1. A method of producing a cellulose ester containing at least one higher aliphatic acyl radical by mixing cellulose with an esterifying liquid comprising the anhydride of an aliphatic acid, an aliphatic acid and a catalyst, at least one of these acids being a higher aliphatic acid; removing during esterification from the reaction mixture containing incompletely esterified undissolved cellulose and dissolved cellulose ester, esterification of which is completed, solution of said cellulose ester; rendering the removed solution incapable of causing degradation of the cellulose ester dissolved therein and continuing esterification in the reaction mixture.

2. A method of producing cellulose acetostearate by mixing cellulose with an esterifying liquid consisting of acetic anhydride, stearic acid, acetic acid and a catalyst; removing during esterification from the reaction mixture containing incompletely esterified undissolved cellu lose and dissolved cellulose ester esterification of which is completed, solution of said cellulose ester; rendering the removed solution incapable of causing degradation of the cellulose ester dis 6 solved therein and continuing esterification in the reaction mixture.

3. In a process for producing a cellulose ester containing at least one aliphatic acyl radical according to the solution type process, the steps of continuously supplying a mixtureof cellulose with an esterifying liquid comprising the anhydride of an aliphatic acid, an aliphatic acid and a catalyst, at least one of these acids being a higher aliphatic acid, to a reaction mixture of celluloseand said esterifying liquid; continuously removing from said reaction mixture containing incompletely esterified, undissolved cellulose and dissolved cellulose ester, esterification of which is completed, solution of said cellulose ester; rendering the removed solution incapable of causing degradation of the cellulose ester dissolved therein and continuing esterification in the reaction mixture.

4. In a process for producing cellulose acetostearate according to the solution type process, the steps of continuously supplying a mixture of cellulose With an esterifying liquid consisting of acetic anhydride, stearic acid, acetic acid, and a catalyst, to a reaction mixture of cellulose and said esterifying liquid; continuously removing from said reaction mixture containing incompletely esterified, undissolved cellulose and dissolved cellulose ester, esterification of which is completed, solution, of said cellulose ester; rendering the removed solution incapable of causing degradation of the cellulose ester dissolved therein and continuing esterification in the reaction mixture.

5. In a process of producing cellulose tripalmitate, the steps of continuously supplying a mixture of cellulose with an esterifying liquid con sisting of monochloracetic acid, palmitic anhydride and carbon tetrachloride together with an esterification catalyst to a reaction mixture of cellulose and said esterifying liquid, continuously removing from said reaction mixture containing,

incompletely esterified, undissolved cellulose and dissolved cellulose ester, esterification of which is completed, solution of said cellulose ester; rendering the removed solution incapable of causing degradation of the cellulose ester dissolved therein and continuing esterification in the reaction mixture.

6. A method as claimed in claim 1, in which removal of the cellulose ester solution is efiected by filtration of the reaction mixture.

7. A method as claimed in claim 1, in which removal of the cellulose ester solution is efiected by subjecting the reaction mixture to centrifuging.

8. A method as claimed in claim 1, in which the separated solution of the cellulose ester is treated with a precipitating agent for said ester immediately after separation.

9. A method as claimed in claim 1, in which the separated solution of the cellulose ester is subjected to a ripening treatment before precipitation.

CHARLES DORAS.

No references cited. 

1. A METHOD OF PRODUCING A CELLULOSE ESTER CONTAINING AT LEAST ONE HIGHER ALIPHATIC ACYL RADICAL BY MIXING CELLULOSE WITH AN ESTERIFYING LIQUID COMPRISING THE ANHDRIDE OF AN ALIPHATIC ACID, AN ALIPHATIC ACID AND A CATALYST, AT LEAST ONE OF THESE ACIDS BEING A HIGHER ALIPHATIC ACID; REMOVING DURING ESTERIFICATION FROM THE REACTION MIXTURE CONTAINING INCOMPLETELY ESTERIFIED UNDISSOLVED CELLULOSE AND DISSOLVED CELLULOSE ESTER, ESTERIFICATION OF WHICH IS COMPLETED, SOLUTION OF SAID CELLULOSE ESTER; RENDERING THE REMOVED SOLUTION INCAPABLE OF CAUSING DEGRADATION OF THE CELLULOSE ESTER DISSOLVED THEREIN AND CONTINUING ESTERIFICATION IN THE REACTION MIXTURE. 